A reciprocating well pump downhole motor (US20150176574) which includes the downhole plunger pump consisting of a fixed barrel and a moving plunger has been proposed. The downhole motor is mounted below the pump and connected with the plunger and causes the plunger to reciprocate. A valve arrangement mounted slightly below the plunger allows the oil-well fluid to flow into the barrel during the upstroke and into the chamber of the oil-well pump below the plunger during its down stroke.
It has previously been proposed to use an oil pumping unit (U.S. Pat. No. 7,316,270) driven by a linear synchronous three-phase motor with rare earth permanent magnets including a motor with the mover reciprocating when the motor is connected to the power mains, and a pump, which has a barrel with suction ducts for oil-well fluid passage and a valve, a movable valve and a piston, a bottom intake valve inside arranged in such a manner that when the mover is reciprocating, the oil-well fluid is being transferred in one direction.
It has previously been proposed to use a pumping unit (RU 2522347 C2) consisting of a downhole part which includes a pump and a linear permanent magnet downhole motor comprising the fixed part (stator) with the winding and the moving part inside (mover) designed so as to allow the mover to reciprocate with regard to stator, the motor housing is linked to the pump case, the mover is linked to the moving part of the pump, the control electronic unit with its power output connected to the stator winding; the control electronic unit comprises the ground-based and downhole units, the motor is fitted with the mover position sensor, the downhole telemetry unit is designed as an inverter in a tight enclosure with standard atmospheric pressure inside, the inverter enclosure is linked to the motor housing, the inverter output is connected to the power circuit and winding through cable glands, the output of position sensor elements is connected to the inverter control unit through additional cable glands and the ground-based unit is designed as series-connected input rectifier, single-phase high-frequency inverting controller and output rectifier.
The unit is characterized in that the high-frequency inverting controller may be designed for galvanic isolation between the output and input rectifier; the first pole of the ground-base unit power output may be connected to the first pole of the downhole inverter power circuit through an insulated cable; the second poles of the ground-based unit output and inverter power circuit are connected with the electrically coupled structural elements of the unit; the analogous poles of the ground-based unit output and downhole inverter power circuit may be connected through insulated two-wire cable; and the inverter control unit may comprise the mover step counter and be designed for reverse operation when the mover reaches the specified number of steps.
The drawback of this unit is a relatively poor reliability.
It has previously been proposed to use a downhole pumping unit (RU 2535288, C2) comprising the linear motor which includes the housing with the concentrically arranged fixed tight stator and a mover inside, the motor cavity formed by the stator, housing and mover is filled with the fluid and the mover is supported by the stator bearing members to provide for reciprocation along the stator longitudinal axis and a pump with the actuator linked to the mover and the fixed part is linked to the motor housing through structural elements designed for venting of the formed pump cavity as well as end plates between pump and motor cavities, arrangements for trapping mechanical impurities within the motor cavity and fine filters located axially in the motor housing between the stator and end plates with their exterior face tightly connected to the housing and the interior face contacts with the mover surface through arrangements for trapping mechanical impurities within the motor cavity.
This unit also lacks proper reliability.
A diaphragm pump downhole linear motor (CN101220806 A) has been also proposed. The downhole linear motor is attached to the diaphragm pump by hydraulic transmission. The invention is characterized in that it comprises the damper, pump piston, plastic expansion joint for the piston, permanent magnet rotor, stator of the linear permanent magnet motor and cylindrical housing. The upper part of the housing is linked to the diaphragm, the diaphragm cavity is divided into two chambers each fitted with an intake ball valve and a discharge ball valve, respectively; the internal cavity of the housing is filled with oil being a hydraulic fluid of the piston pump which has proper lubricating properties and provides proper sealing from the diaphragm to the expansion joint; the spring-loaded flexible assembly, piston pump, damper, rotor of the linear permanent magnet motor, stator of the linear permanent magnet motor and elastic expansion joints are mounted below the diaphragm.
The drawback of this engineering concept is a relatively poor reliability of the diaphragm and damper which is a compensator of the volume within the downhole linear motor during its operation and provides no impact protection in the extreme upper and lower points of the piston.
A reciprocating downhole pump with the gas separator located at its end (US20060002808 A1) has been proposed. The gas separator forms a cavity. The cavity has orifices for fluid passage during reciprocation of the pump plunger. The orifices are sized so as the fluid enters the pump intake while the gas is separated from the fluid in the formed cavity.
The drawback of this engineering concept is increased dimensions and weight of the unit due to external gas separator since the reciprocating downhole pump and the gas separator form two separate units.
A linear motor driven oilfield pump (US20080264625 A1) has been proposed. The linear motor moves the crankshaft or hydraulic gear for driving the pump plunger.
The drawback of this engineering concept is a poor bending resistance of the plunger since the plunger housing diameter is greater than that of the plunger and provides no plunger bending resistance.
It has previously been proposed to use a downhole pumping unit (U.S. Pat. No. 5,960,875 A) comprising an electric pump which includes the linear motor consisting of a stator (fixed part) and a mover (moving part) which can be moved under the effect of the electromagnetic field generated by the stator, a pump piston is moved inside the stator by the linear motor and characterized in that the motor mover and the piston are located inside the electric pump stator and form a single moving component of the linear motor.
The drawback of this unit is a relatively low power performance, great power losses due to large magnetic gap between magnetic sections of the mover and stator. This unit has a relatively low power since the magnetic sections of the mover are made of soft magnetic materials to provide for mover removal. The mounting of additional sensors such as intake pressure and temperature sensors and motor temperature sensors requires the supplementary communication lines of the ground-based unit.
The most technically similar concept to the proposed one is a unit (RU 2521530, C1) comprising a displacement pump and a downhole linear motor which includes the fixed part (stator) with the winding and the moving part inside (mover) designed so as to allow the mover to reciprocate with regard to stator, the motor cavity is vented, the motor housing is linked to the pump case, the mover is linked to the moving part of the pump through the rod, the stator has the cylindrical and end sealing elements for the stator; the motor cavity is vented through filter and linked with the pump cavity through the packing between the rod and housing, the motor stator has longitudinal through conduits between the external face of the winding and inner face of the motor housing which connect the cavities on either end sides of the stator.
This unit is characterized in that it may be equipped with the supplementary rod identical to the first one arranged on the other side of the mover and vented through additional packing in a housing, the filter is designed as a fine filter, the tubular members made of high thermal conductivity material may be arranged in longitudinal through conduits with the ends of tubular members tightly connected to the end packing elements of the stator.
The most similar engineering concept has a relatively poor reliability and low power performance.
The object of the present invention is to increase the reliability and improve the power performance of the unit by overcoming the above mentioned drawbacks of the previous engineering concepts.